Elasto-Plastic Constitutive Model Considering the Influences of Soil Structure and Anisotropy

2013 ◽  
Vol 405-408 ◽  
pp. 478-482
Author(s):  
Guang Qin Cui ◽  
Zeng Rong Liu ◽  
Chen Guang Ma
Keyword(s):  
Constitutive Model ◽  
Soil Structure ◽  
Structural Parameters ◽  
Natural Soil ◽  
Strain Behavior ◽  
Modified Cam Clay ◽  
Practical Engineering ◽  
Evolution Laws ◽  
Geotechnical Tests ◽  
Anisotropic Tensor

Structure and anisotropy are two fundamental aspects of natural clays. They cant be ignored because of their significant influences on soils strength and stress-strain behavior, etc. Therefore, anisotropic tensor and structural parameters are introduced in Modified Cam Clay Model which is only suitable for isotropic remolded clays, and evolution laws of them are given in this paper. Thus, an elasto-plastic constitutive model considering the influences of natural soil structure and anisotropy is established. Most parameters involved in this model have explicit physical meaning and are easily determined through geotechnical tests, which makes this model more flexible, practical and applicable to practical engineering.

scholarly journals Destructuration of saturated natural loess: From experiments to constitutive modeling

2020 ◽  
pp. 105678952093930
Author(s):  
Yukai Fu ◽  
Zhiwei Gao ◽  
Yi Hong ◽  
Tonglu Li ◽  
Akhil Garg
Keyword(s):  
Constitutive Model ◽  
Constitutive Modeling ◽  
Soil Structure ◽  
Triaxial Compression ◽  
Structural Effect ◽  
Triaxial Tests ◽  
Natural Soil ◽  
Special Focus ◽  
Compression Tests ◽  
Natural Loess

It has been well recognized that unsaturated natural loess shows significant volume contraction upon wetting due to its metastable internal structure. But the structural effect on stress–strain relationship of saturated natural (undisturbed) loess is much less explored. Few attempts have been made in proposing a constitutive model for saturated natural loess. This study presents both laboratory tests and constitutive modeling of a saturated natural loess, with special focus on the structural effect and evolution of structure damage during loading. Oedometer and drained triaxial compression tests have been carried out on undisturbed and remolded saturated loess samples. It is found that the natural soil structure has dramatic influence on mechanical behavior of loess, including the compressibility, dilatancy, and shear strength. Destructuration, which is the damage of soil structure with deformation, is observed in both oedometer and triaxial tests. A constitutive model is proposed for saturated loess based on the experimental observations. The model is established within the theoretical framework of subloading and superloading surface concepts. Destructuration of loess is assumed to be affected by both plastic volumetric and shear strain. A new method for determining the initial degree of structure is proposed. The model can reasonably predict the compression and shear behavior of both undisturbed and remolded saturated loess.

Determination of Parameter in SYS Cam-Clay Model of Ultra-Soft Clay

2015 ◽  
Vol 744-746 ◽  
pp. 470-473
Author(s):  
Bin Bin Xu ◽  
Toshihiro Noda
Keyword(s):  
Constitutive Model ◽  
Soil Structure ◽  
Soft Clay ◽  
Numerical Results ◽  
Plastic Model ◽  
Clay Model ◽  
The World ◽  
Practical Engineering ◽  
Cam Clay

Parameter analyses in the constitutive model determine the precision of numerical results. Cam-clay model is the first elasto-plastic model in the world and widely used in the practical engineering. SYS Cam-clay model is proposed based on Cam-clay model by incorporating the concept of overconsolidation, soil structure and anisotropy. There are two groups of parameters in this model, elasto-plastic parameters that are exactly same as those in Cam-clay model and evolutional parameters that decide the variation of overconsolidation, soil structure and anisotropy. The detailed process to determine the parameters is introduced step by step.

Micromorphology of soil structure - Description, quantification, application

Soil Research ◽  
1991 ◽  
Vol 29 (6) ◽  
pp. 777 ◽  
Author(s):  
AJ Ringrose-Voase
Keyword(s):  
Soil Structure ◽  
Pore Space ◽  
Structural Parameters ◽  
Thin Sections ◽  
Physical Measurements ◽  
Undisturbed Samples ◽  
Structure Description ◽  
Management Techniques ◽  
Pore Types ◽  
Soil Behaviour

Micromorphological observation can provide insights into soil structure and aid interpretation of soil behaviour. Undisturbed samples are taken in the field and impregnated. They are used to prepare thin sections or images of the macropore structure using fluorescent photography. Sections can also be obtained at macro, meso and submicroscopic scales. The various elements of soil structure observed micromorphologically can be classified into pore space, physical, distribution and orientation fabrics, and associated structures. Examples of the importance of features in each category are given. Image analysis, especially when computerized, provides a way of parameterizing micromorphological observations. To date it has been used primarily on images of macropore space at the meso and microscopic scales. Such images can be digitized and segmented to show pore space and solid. The pore space can be allocated to pore types. This aids the estimation of 3-D parameters from I-D and 2-D measurements made on the image using stereology. Various ways of using structural parameters to compare structures are discussed. Applications for micromorphological observations, especially when quantitative, include comparison of structures formed by different management techniques. Structural measurements can aid interpretation of soil behaviour as described by physical measurements. They also have a role in estimating the representative elementary volume, on which physical measurements should be made, and in calibrating field estimates of soil structure.

Implementation of a soil-structure interface constitutive model for application in geo-structures

2019 ◽  
Vol 116 ◽  
pp. 714-731 ◽  
Author(s):  
Miad Saberi ◽  
Charles-Darwin Annan ◽  
Jean-Marie Konrad
Keyword(s):  
Constitutive Model ◽  
Soil Structure

scholarly journals INFLUENCE OF CLAYEY SOIL STRUCTURE ON ITS MODULUS OF STIFFNESS

1999 ◽  
Vol 5 (2) ◽  
pp. 108-115
Author(s):  
Antanas Alikonis
Keyword(s):  
Soil Structure ◽  
Clayey Soil ◽  
Deformation Modulus ◽  
Natural Soil ◽  
Logarithmic Scale ◽  
Compression Curve ◽  
Engineering Structures ◽  
Compacted Soil ◽  
Deformation Properties ◽  
Compressibility Coefficient

Disturbance of soil structure influences its density, strength and deformation properties. Among other cases soil structure could be disturbed by compacting it. It is possible to increase deformation properties of sand or gravel by compacting them. However, for clay soils deformation properties may increase if they are compacted. Differences of settlements of a building depends on the different deformation properties of the artificially placed and compacted soils beneath the foundations. Different values of stiffness modulus are used for the structural design of the buildings which are constructed on the soils with different compressibility. Coefficient of changeability of soil compression (1) was used. It may be calculated as a ratio of maximum and minimum values of deformation modulus, or according to the maximum and minimum values of coefficient of relative compressibility (3). Coefficient of the relative compressibility of soil can be calculated depending on the maximum and minimum values of tip resistence from CPT test (5). According to the coefficient of the relative compressibility we could estimate whether the soil is uniform, nonuniform or extremely non-uniform. It is important for the design of civil engineering structures. Mechanical properties of soils may be back-calculated using theoretical values of settlements and loads. Most frequently within the building layout area soils are natural and artificially compacted. For a compacted soil it is possible to draw compression curve in semi-logarithmic scale using compression curve of the same natural soil and the void ratio of the artificially placed and compacted soil. Thus we can determine compressibility of the soil with disturbed or undisturbed structure. Using parameters of soil compressibility, we can determine the coefficient of the relative compressibility, maximum and minimum values of settlement and modulus of stiffness.

Thermodynamic-based cross-scale model for structural soil with emphasis on bond dissolution

2021 ◽  
Author(s):  
Wei Zhang ◽  
Jia-qiang Zou ◽  
Kang Bian ◽  
Yang Wu
Keyword(s):  
Constitutive Model ◽  
Bond Strength ◽  
Scale Model ◽  
Triaxial Tests ◽  
Natural Soil ◽  
Engineering Practice ◽  
Compression Tests ◽  
Strength Deterioration ◽  
Decomposed Granite ◽  
Completely Decomposed Granite

The immersion weakening effect of natural soil has always been a difficult problem encountered in geotechnical engineering practice. The bond dissolution is a common cause of soil strength deterioration, which remains not well understood yet. In this study, a thermodynamic-based constitutive model of structural soils based on the α model is first established, considering the bond strength by modifying the yield surface size and gradually reducing the bond strength with the development of plastic strain. Furthermore, by taking the meso-mechanisms of bond dissolution into account, the evolution rule of the free energy during the bond dissolution process is derived based on a homogenization approach, and a thermodynamic-based constitutive model of structural soil with bond dissolution is thereafter developed. By comparing with the results of one-dimensional compression tests and conventional triaxial tests, the model is verified to be capable of reflecting the gradual destructuration process of soil while loading. The comparison with triaxial test results of completely decomposed granite after different immersion durations and parametric studies show that based on the cross-scale energy equivalence, the model can well reflect the strength deterioration characteristics of completely decomposed granite with bond dissolution mechanisms at the mesoscale fully considered.

scholarly journals Dynamic Stiffness and Damping Characteristics of a Shaft Damping Ring: A Combined Hyperelastic and Viscoelastic Constitutive Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Miaomiao Li ◽  
Jian Chen ◽  
Rupeng Zhu ◽  
Cheng Duan ◽  
Shuai Wang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Constitutive Models ◽  
Operating Conditions ◽  
Uniaxial Tensile ◽  
Bending Vibrations ◽  
Damping Characteristics ◽  
Shaft System ◽  
Stiffness And Damping

At higher velocities, the helicopter tail transmission system encounters notable difficulties due to excessive bending vibrations. The shaft damping ring installed on the shaft system was shown to effectively suppress the shaft system vibrations. In this paper, the dynamic stiffness and damping characteristics of polyurethane shaft damping rings were studied using hyperelastic and viscoelastic constitutive models. The constitutive model and the damping ring material parameters were determined using uniaxial tensile and double-shear frequency scanning tests. Based on the test results, the dynamic damping ring characteristics were simulated and verified by dynamic stiffness tests; the influence of structural parameters and operating conditions on the dynamic stiffness and damping characteristics of the damping ring were obtained. The results provide a theoretical basis for the design of shaft systems with reduced sensitivity to vibrations.

Thermodynamic-Based Modified Cam-Clay Constitutive Model Considering the Effect of Fabric

2011 ◽  
Vol 71-78 ◽  
pp. 1073-1078
Author(s):  
Xiao Xia Guo ◽  
Bo Ya Zhao
Keyword(s):  
Constitutive Model ◽  
Granular Materials ◽  
Yield Surface ◽  
True Stress ◽  
Stress Space ◽  
Volume Strain ◽  
Hardening Rule ◽  
Modified Cam Clay ◽  
Fabric Tensors ◽  
Cam Clay

In order to construct a constitutive model taking into the effect of both the fabric tensors and their evolution modes, this paper links modern ideas of thermomechanics opinion to the theory of fabric tensors. The anisotropic dissipation incremental function of modified Cam-clay constitutive model considering the effect of fabric characteristic can be obtained by establishing the relation between microstructure and plastic volume strain. After discussing the yield surfaces in the dissipative and the true stress space from the viewpoint of the evolution mode of the fabric tensors, the results indicate that the slope of the normal consolidation line and the critical state line will be governed by changes of void fabric. The model successfully captures most salient behaviors of granular materials related to fabric issues. In the dissipative stress space, the void of granular materials can rearrange and show more anisotropic. In the true stress space, fabric not only affects the deflection of the yield surface, but also affects the hardening rule.

scholarly journals Uniform Nonlinear Constitutive Model and Parameters for Clay in Different Consolidation Conditions Based on Regression Method

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Tao Cheng ◽  
Keqin Yan ◽  
Huazhi Zhang ◽  
Xianfeng Luo ◽  
Shengfang Li
Keyword(s):  
Constitutive Model ◽  
Initial Conditions ◽  
Constitutive Relations ◽  
Test Sample ◽  
Maximum Relative Error ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Constitutive Model ◽  
Isotropic Consolidation

The nonlinear constitutive relations of clay are investigated considering different initial conditions. Highly compressible clay is selected as the test sample. Two groups of tri-axial compression tests are performed, respectively, afterK0consolidation and isotropic consolidation. On the basis of the framework ofE~vmodel, a uniform nonlinear constitutive model is proposed by fitting the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison between the experimental stress-strain curves and the results predicted by the constitutive model is made. It is shown that the prediction is reasonable, which can reflect the stress-strain behavior of the soil under theK0consolidation and isotropic consolidation conditions. The maximum relative error of the two series of curves is not remarkable, less than 6%.

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